Wireless telecommunication system

ABSTRACT

A method and device for processing a message in a UE (user equipment) mobile telecommunications device. The UE device receives a CUC (Cell Confirmation Confirm) message and, in response, determines whether the UE device has an empty cell identifier variable. If so, The UE device then determines whether the CUC message includes a cell identifier and, if not, and if the CUC message would cause the UE device to enter a state that requires the UE device to respond to the message before entering the a next state, carrying out at least one further step such as setting INVALID_CONFIGURATION to TRUE in the UE device prior to entering the state.

FIELD OF THE INVENTION

The present invention relates to the field of telecommunications andparticularly to the area of wireless telecommunication systems.

BACKGROUND OF THE INVENTION

In a typical cellular radio system, mobile user equipment (UE)communicates via a radio access radio network (RAN) to one or more corenetworks. User equipment (UEs) comprises various types of equipment suchas mobile telephones (also known as cellular or cell phones), lap topswith wireless communication capability, personal digital assistants(PDAs) etc. These may be portable, hand held, pocket sized, installed ina vehicle etc and communicate voice and/or data signals with the radioaccess network.

The radio access network covers a geographical area divided into aplurality of cell areas. Each cell area is served by at least one basestation, which may be referred to as a Node B. Each cell is identifiedby a unique identifier which is broadcast in the cell. The base stationscommunicate at radio frequencies over an air interface with the UEswithin range of the base station. Several base stations may be connectedto a radio network controller (RNC) which controls various activities ofthe base stations. The radio network controllers are typically connectedto a core network.

An example of a radio access network is the Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access Network(UTRAN). UMTS is a third generation mobile communication system andessentially relates to a wide band code division multiple access(W-CDMA) system.

W-CDMA technology allows simultaneous communication between userequipment and a plurality of base stations using a common frequencyband. Signals occupying a common frequency band are discriminated in thereceiving base station through spread spectrum CDMA waveform propertiesbased on the use of a high speed, pseudo-noise (PN) code. These highspeed PN codes are used to modulate signals transmitted from the basestations and the user equipment. A transmitting station uses a PN codeto produce signals that can be separately demodulated at a receivingstation. In CDMA therefore a user equipment unit need not switchfrequency when handover of the connection is made from one cell toanother. Thus, a destination cell can support a connection to the userequipment at the same time as the original cell continues to provideservice. Since the UE is always communicating through at least one cellduring hand over, there is no disruption to the call.

There are several interfaces defined in the UTRAN. In some instances aconnection involves both a serving or source RNC (SRNC) and a target ordrift RNC (DRNC), with the SRNC controlling the connection but with oneor more diversity legs of the connection being handled by the DRNC. UMTShas both common transport channels and dedicated transport channels.Common transport channels include the random access channels (RACH), theforward access channel (FACH), the common packet channel (CPCH) and thedownlink shared channel (DSCH). Dedicated transport channels include thededicated channel (DCH). These transport channels are described forexample in one or more of the following specifications:

-   -   ETSI TS 125.211 Version 3.12.0 “Physical Channels and Mapping of        Transport Channels on to Physical Channel (FDD)”;    -   ETSI TS 125.221 Version 3.11.0 “Physical Channels and Mapping of        Transport Channels on to Physical Channel (TDD)”;    -   ETSI TS 125.331 Version 3.15.0 “Radio Resource Control (RRC)        Protocol Specification.

When switching from a dedicated to a common channel in UMTS, the UE isassigned a temporary identifier known as C-RNTI (Cell Radio NetworkTemporary Identifier). This temporary identifier C-RNTI is specific to acell and is valid in the cell where the UE uses resources. The C-RNTI isused to distinguish between different user equipment in that cell.

When switching from dedicated channels to common channels, the networkcan assign the radio resources to be used only if the UE is in a cellunder control of the serving SNC (SRNC). In other words, if the UE is ina cell under the control of a drift RNC (DRNC) rather than SRNC, it isnot possible for the network to assign the radio resources to be usedwhen switching from dedicated channels to common channels. This resultsin longer signalling sequences between the UE and the network as well asadditional delay when switching from dedicated channels to commonchannels. The UE itself must obtain the temporary identifier C-RNTI byadditionally signalling between the UE and UTRAN before continuing tocommunicate with the network. Furthermore, the lack of informationregarding which range of resources to use means that the UE needs todetect and read information about the range of resources and thebroadcast channel in the cell before accessing the cell. This againincurs additionally delay when switching from dedicated channels tocommon channels.

BRIEF DESCRIPTION OF DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIG. 1 shows a schematic diagram of a radio access network system;

FIG. 2 shows the components of a user equipment used with the radioaccess network system of FIG. 1;

FIG. 3 illustrates the cell update procedure used with a radio accessnetwork system as shown in FIG. 1;

FIG. 4 is a flow chart illustrating the operation of a first embodimentof a system;

FIG. 5 is a flow chart showing a second embodiment of the system;

FIG. 6 is a flow chart showing a third embodiment of the system; and

FIG. 7 is a flow chart showing a fourth embodiment of the system.

The needs identified in the foregoing Background, and other needs andobjects that will become apparent from the following description, areachieved by, in one aspect, a method for processing a message in amobile telecommunications device. The method comprises, on receipt of aCell Update Confirm (CUC) message, determining whether the device has anempty cell identifier variable e.g. C_RNTI. When the device has an emptycell identifier variable, it is determined whether the CUC messageincludes a new cell identifier e.g. C-RNTI. If this is the case, and theCUC message would cause the device to enter a state which requires theUE to respond to the message before entering the state, at least onefurther step is carried out prior to entering the state.

In other aspects, the invention encompasses apparatus and acomputer-readable medium configured to carry out the foregoing steps. Inparticular, the method may be implemented in a mobile telecommunicationsdevice, with or without voice capabilities, or other electronic devicessuch as handheld or portable devices.

FIG. 1 shows an overview of the radio access network (UTRAN) used in aUMTS system. The network as shown in FIG. 1 comprises three RadioNetwork Subsystems (RNS) 2. Each RNS has a Radio Network Controller(RNC) 4. Each RNS 2 has one or more Node B 6 which are similar infunction to a Base Transmitter Station of a GSM radio access network.User Equipment UE 8 may be mobile within the radio access network. Radioconnections (indicated by the straight dotted lines in FIG. 1) areestablished between the UE and one or more of the Node Bs in the UTRAN.

A radio network controller RNC controls the use and reliability of theradio resources within the RNS. Each RNC is also connected to a 3Gmobile switching centre 10 (3G MSC) or a 3G serving GPRS support node 12(3G SGSN).

An RNC controls one or more Node B's. An RNC plus its Node B's togethermake up an RNS. A Node B controls one or more cells. Each cell isuniquely identified by a frequency and a primary scrambling code(primary CPICH in FDD, primary CCPCH in TDD).

Generally in UMTS a cell refers to a radio network object that can beuniquely identified by a UE from a cell identifier that is broadcastover geographical areas from a UTRAN access point. A UTRAN access pointis a conceptual point within the UTRAN performing radio transmission andreception. A UTRAN access point is associated with one specific celli.e., there exists one UTRAN access point for each cell. It is theUTRAN-side end point of a radio link.

C-RNTI, the Cell Radio Network Temporary Identity, is a UE identifierallocated by the controlling RNC and it is unique within one cellcontrolled by the allocating CRNC. C-RNTI can be reallocated when a UEaccesses a new cell with a cell update procedure. C-RNTI is used as a UEidentifier in DCCH/DTCH common channel messages on the radio interface.

FIG. 2 shows a schematic diagram of various components of UMTS userequipment. The UE 8 includes an antenna 80 and a transceiver 82 fortransmitting and receiving radio signals. In the Time Division Duplux(TDD) mode of UMTS, the transceiver 82 may use a rake receiver toestablish the signal to be operated on by the UE. The transceiver 82 isconnected to a processor 84 which processes the signals received by andsent by the transceiver. The processor 84 has connections to memory 86and a user interface device 88 (such as a keyboard and/or a screen).FIG. 2 only shows the main components of the UE. Clearly the UE willinclude other components which are not shown but which are not relevantfor the present understanding.

FIG. 3 shows the cell update procedure in UMTS. Firstly the UE sends acell update to the UTRAN. ETSI TS 125.331 Version 03.15.00 Section8.3.1.5 describes what occurs at the UTRAN when the UTRAN receives acell update message from a UE. Among other things, the UTRAN transmits acell update confirm (CUC) message. ETSI TS 125.331 Version 03.15.00Section 8.3.1.6 describes the operation of the UE on reception of a cellupdate confirm message from the UTRAN. The UE may in response send aPhysical or Transport Channel Configuration Complete message or anyother suitable message or possibly no response message.

FIG. 4 is a flow diagram illustrating one example of how the UE mayreact to receiving a CUC message.

On receipt (step 401) of a cell update confirm message, firstly the UEchecks (step 402) whether the C_RNTI variable of the UE is empty. Ifnot, the UE carries out further processes (step 403) which will not bediscussed further. However, should the C_RNTI variable be empty, the UEthen checks whether a new C-RNTI is included in the received CUC message(step 404). If a new C-RNTI is included in the CUC message, the UEcontinues with other processes (step 403) which will not be discussedfurther. However, should the CUC not include a new C-RNTI then the UEchecks whether the CUC message would place the UE in a state requiring aresponse prior to entering the state (step 405). If this is not thecase, the UE continues to further processes which will not be discussedfurther. However, if the CUC message does place the UE in a state thatrequires a response prior to entering the state, the UE takes furtheraction as set out in step 406.

As shown in FIG. 4, this step 406 comprises setting the variableINVALID_CONFIGURATION to TRUE thus the processing of the CUC message isaborted. The UE then may continue with further processes (step 407) suchas sending a subsequent cell update message to the UTRAN or returning toidle. This decision may depend on the value of V302 and N302 asdescribed in Section 8.3.1.9 of ETSI TS 25.331 Version 3.15.0.

FIG. 5 shows a further embodiment. Steps 501, 502, 503, 504 and 505 arethe same as steps 401 to 405 described with reference to FIG. 4.However, as shown in FIG. 5, in this embodiment when a message wouldplace the UE in a state requiring response prior to entering the state(step 505), then the UE sends a new cell update message with the causeset to “cell reselection”.

FIG. 6 shows a further embodiment in which steps 601 to 605 are the sameas steps 401 to 405 as described with reference to FIG. 4. However, whenthe CUC message places the UE in a state requiring response prior toentering the state, in this embodiment the UE acts on the cell updateconfirm message but does not respond to the UTRAN (step 606).

FIG. 7 shows yet a further embodiment in which step 701 to 705correspond to steps 401 to 405 of FIG. 4. However, when the messageplaces the UE in a state requiring a response prior to entering thestate, the UE simply ignores the CUC and takes no action in response toreceipt of the CUC.

Such operations in particular are applicable to ETSI Standard TS 125.331version 3.15.0 (and other similar CDMA standards) which may be amendedto implement these proposals. For instance, section 8.3.1.6 of ETSI TS125.331 Version 3.15.0 may be amended as follows:

If the UE after state transition enters URA_PCH or CELL_PCH state, andif a response message is to be transmitted according to subclause8.3.1.7, it should/shall:

-   -   1>if the contents of the variable C_RNTI are empty:    -   2>set the variable INVALID_CONFIGURATION to TRUE.

An alternative amendment to the standard is as follows:

If the UE after state transition enters URA_PCH or CELL_PCH state, andif a response message is to be transmitted according to subclause8.3.1.7; and

-   -   1>the contents of the variable C_RNTI are empty:        the UE shall check the value of V302 and continue.

In the first of these situations, rather than accepting a CUC command,CUC processing by the UE is aborted and the variableINVALID_CONFIGURATION is set to TRUE. This results in a subsequent cellupdate message being sent to the UTRAN or the UE returning to idledepending on the values of V302 and N302 as described in Section 8.3.1.9of the standard. Thus, on receipt of the cell update confirm message, itis determined whether the message contains a C-RNTI and whether themessage places the UE in a state that requires a response prior toentering the state. If both of these are true, the processing of thecell update confirm message may be aborted and the variableINVALID_CONFIGURATION be set to TRUE. A subsequent cell update messagemay be sent to the UTRAN or other processes as described above.

In the alternative, on receipt of a cell update confirm message, when itis determined that the message does not contain a C-RNTI and it isdetermined that the variable C_RNTI is empty. If so it is determinedwhether the message places the UE in a state which requires responseprior to entering that state. If it does, the cell update confirmmessage is processed by the UE and the UE then continues with thefurther processes for example sending subsequent cell update message tothe UTRAN or returning to idle depending on the values of V302 and N302as described in Section 8.3.1.6 of the standard for the case where CUCplaces the UE in Cell_FACH with the variable C_RNTI empty.

It is to be noted that the methods as described have shown steps beingcarried out in a particular order. However, it would be clear to aperson skilled in the art that the order of the evaluation is immaterialwith respect to the operation of the method. For instance, the devicemay check whether a C-RNTI is included in the CUC and/or whether themessage places the UE in a state requiring a response prior to enteringthe state before determining whether the UE has an empty C_RNTIvariable. The ordering of the steps as described herein is not intendedto be limiting.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader spirit and scope of the invention. Thespecification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense. Any features as claimedmay be used in combination or separately.

1. A method of processing a message in a User Equipment (UE) mobiletelecommunications device, the method comprising: receiving a CellUpdate Confirm (CUC) message at the UE device; determining, by the UEdevice, whether the UE device has an empty cell identifier variable;subsequent to determining that the UE device has an empty cellidentifier variable, determining by the UE device whether the receivedCUC message includes a value for the cell identifier; when the CUCmessage does not include a value for the cell identifier and the CUCmessage would cause the UE device to enter a state that requires the UEdevice to respond to the message before entering the state, settingINVALID_CONFIGURATION to TRUE in the UE device prior to entering thestate.
 2. A method according to claim 1 further comprising sending acell update message to the network.
 3. A method according to claim 1further comprising returning to an idle state.
 4. A method according toclaim 1 wherein the cell identifier variable is C_RNTI and the value ofthe cell identifier is C-RNTI.
 5. A User Equipment (UE) device includingapparatus for processing a message in a mobile telecommunicationssystem, the apparatus being arranged to: receive a Cell Update Confirm(CUC) message from a network; determine whether the UE device has anempty C_RNTI variable; when the UE device has an empty C_RNTI variable,determine whether the received CUC message includes a C-RNTI; when theCUC message does not include a C_RNTI and the CUC message would causethe UE device to enter a state that requires the UE device to respond tothe message before entering the state, setting INVALID_CONFIGURATION toTRUE prior to entering the state.
 6. Apparatus according to claim 5wherein the apparatus is further arranged to send a cell update messageto the network subsequent to setting the INVALID_CONFIGURATION to TRUE.7. Apparatus according to claim 6 wherein the cell update messageincludes a field indicating that the cause for the cell update messageis cell reselection.
 8. Apparatus according to claim 5 wherein theapparatus is further arranged to return to the idle state subsequent tosetting the INVALID_CONFIGURATION to TRUE.
 9. Apparatus according toclaim 5 wherein the apparatus is further arranged to act on the cellupdate confirm message without transmitting a response to the network.10. A mobile telecommunication device incorporating apparatus accordingto any of claim 5 and 6-9.